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#85730 - 08/02/03 06:34 AM Voltages used for branch circuit calculations  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Based upon the National Electrical Code:

Question:

How many 125 volt, 15 ampere duplex receptacles are allowed to be installed on a 20 ampere, 115 volt branch circuit in a commercial building?

A. 11
B. 10
C. 12
D. 13


Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#85731 - 08/02/03 07:46 AM Re: Voltages used for branch circuit calculations  
zapped208  Offline
Member
Joined: Feb 2003
Posts: 196
Somewhere in USA
B. 10


Shoot first, apologize later.....maybe

#85732 - 08/02/03 09:53 AM Re: Voltages used for branch circuit calculations  
Fred  Offline
Member
Joined: Apr 2001
Posts: 449
Straughn, IN 47387
C. 12


#85733 - 08/02/03 11:03 AM Re: Voltages used for branch circuit calculations  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
10 Receptacles.

115 VAC × 20 AMPS = 2300 VA

80% of 20 AMP Ckt (Gen. Purpose Recept. Ckt. NEC art. 210-21 and 210-23):

2300 VA × 0.8 = 1840 VA.

180 VA per Duplex Receptacle:

1840 VA ÷ 180 VA = 10.2222

10.222 Receptacles per circuit

That would be 10 complete Duplex Receptacles, and parts of a Duplex Receptacle - to make it 0.222 of a Duplex Receptacle
[Linked Image]

Easier to just round off to 10 Receptacles! 0.222 of a Receptacle is not useful!!!
<joke> [Linked Image]

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#85734 - 08/02/03 11:25 AM Re: Voltages used for branch circuit calculations  
Ron  Offline
Member
Joined: Mar 2002
Posts: 582
White Plains, NY
Wow, this question has made it rounds to 2 or 3 forums already.
Section 220.2(a) 2002 NEC®, or 220-2(a) 1999 NEC® and the first words, "Unless other voltages are specified ...".
Read the original question again. I missed it the first time.


Ron

#85735 - 08/02/03 12:05 PM Re: Voltages used for branch circuit calculations  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
Who is permitted by the code to specify a voltage. Why couldn't someone specify 126 volts and install 14 duplex receptacles?

Scott,
The 80% does not apply so the answer based on the 115 volts is 12, but I don't think that anyone has the right under the code to specify a voltage for this circuit. It is my opinon that the calculation should be based on 120 volts.
Don


Don(resqcapt19)

#85736 - 08/02/03 05:09 PM Re: Voltages used for branch circuit calculations  
George  Offline
Member
Joined: Feb 2002
Posts: 375
I will say 10, 11, 12, or 13.

The max is 13. 120*20/180

You can only specify the voltage if you control the voltage.


#85737 - 08/02/03 10:25 PM Re: Voltages used for branch circuit calculations  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
George, controling the voltage wouldn't be a problem, and if an aspiring young Jman exam taker answered anything but 12, he or she missed the question.

Roger


#85738 - 08/03/03 11:50 AM Re: Voltages used for branch circuit calculations  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
Roger,
So if I specified a voltage of 126 and installed 14 duplex receptacles, the inspector would have to pass my installation?
I'll say what I have posted on other forums. The question is bogus. The installer does not have the right to specify the voltage.
Don

[This message has been edited by resqcapt19 (edited 08-03-2003).]


Don(resqcapt19)

#85739 - 08/03/03 12:29 PM Re: Voltages used for branch circuit calculations  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
Don,
allbeit 'code' spec's are 'nominal', would one say they rely on the manufacturer's listings?


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